Field of the Invention
This invention relates to a voltage controlling discharge tube, and more particularly to a gas-filled discharge tube to be used as a series-gap in an ignition device of an automobile engine and the like.
This invention relates to a high-tension cable device, and more particularly, to a high-tension cable device which is preferable for an ignition device having a series-gap for an automobile engine and the like.
Although the ignition device in an automobile engine and the like is constructed such that a high voltage is applied to an ignition plug to generate a spark, there is proposed a so-called ignition device having a series-gap having a discharge clearance in series with an ignition plug in order to make an accurate control of an ignition time as well as to prevent occurrence of smoking at the ignition. As such a series-gap forming device, it is already known to provide a discharge tube having discharge electrodes at both ends of the cylinder and having inert gas filled therein.
As the correct controlling of the ignition time of the ignition plug by using the series-gap discharge tube, it is necessary to have a certain higher degree of a discharge starting voltage of the discharge tube as compared with that of the ignition plug. Then, in order to increase the discharge starting voltage while keeping a small-sized shape of the discharge tube, it is already known to provide a method for increasing a pressure of the filled inert gas.
In the prior art, in case of assembling the discharge tube, it has been employed to airtightly connect the cylinder made of electrical insulating material enduring against a high voltage, for example, glass or ceramics and the like with some metallic electrode terminals by using glass frit or metallic solder and the like. In such a process, it has been suggested that the process is carried out in a vacuum electric furnace in order to keep quality of the discharge tube. To the contrary, the assembling the gas-filled discharge tube requires to change-over atmosphere within the electric furnace from its vacuum state to gas atmosphere. Filling high pressure gas requires an anti-voltage characteristic of the electric furnace, resulting in that the assembling device is not only large in size and complex but also its number of steps is increased and is not economical.
In turn, since a high vibration is always applied to the ignition device in the automobile engine and the like, it is necessary for the high voltage cable device supplying a high voltage to the ignition plug to endure against vibration and further the series-gap discharge tube to be assembled in the high voltage cable device and its connecting device are required to endure against vibration.
It is already known to provide an ignition device in which a so-called series-gap is arranged in series with an ignition plug so as to prevent sooting at the ignition plug caused by adhesion of carbon and the like (refer to Jap. U. M. Laid-Open No. Sho 63-101486).
FIG. 4 illustrates a high-tension cable device C to be used in this type of prior art ignition device, in which a plug cap 25 fixed to an extreme end of a high-tension cable 24 in communication with the power supplying side is removably attached to a terminal 23 of the ignition plug 22 threadably fitted to the cylinder head 21 of the engine. The plug cap 25 is composed of a substantial cylindrical casing 26 and then a connector terminal 27 capable of being engaged with the terminal 23 of the ignition plug 22 and a power supplying terminal 28 connected to an end part of the high-tension cable 24 are spaced apart longitudinally within the casing 26 in opposition to each other.
A discharge tube 29 forming a so-called series gap S is assembled within the casing 26 as an additional function part. The electrode terminals 30 and 31 of the discharge tube 29 are fitted and contacted with the connector terminal 27 and the power supplying terminal 28 of the casing 26.
Since the aforesaid high-tension cable device C is directly fixed to the engine, there is a possibility that the discharge tube 29 assembled in the aforesaid casing 26 is damaged by a certain vibration of the engine and the like. Due to this fact, it is already proposed that a clearance 32 formed between the aforesaid discharge tube 29 and the casing 26 is filled with filler material 33 such as thermosetting resin and the like so as to protect the discharge tube 29 against vibration.
Under a circumstance described above, the present invention may provide a gas-filled discharge tube which is endurable against vibration and applied to a series-gap unit.
An object of the present invention is accomplished by a gas-filled discharge tube having a pair of electrodes at both ends of an electrical insulating cylinder and having gas filled therein characterized in that a cylindrical protection terminal is fitted to the gas-charging pipe passed through the electrode, said electrode, said gas-charging pipe and said protection terminal are connected by electrical conductive binder filled in a clearance of these elements.
Since the gas-filled discharge tube of the present invention is made in such a way as, for example, it is assembled in vacuum, gas having desired composition is fed into the gas-charging pipe passed through the electrode to become a desired pressure and then the gas-charging pipe is sealed, its sealed end is projected out of an external end surface of the electrode. At the sealed end is fitted a cylindrical protective terminal and also connected the electrode, so that when it is assembled as a series-gap unit to a high voltage cable to be fitted to an ignition plug, for example, a positive assembling operation which is highly durable against vibration can be attained.
However, since the aforesaid filler material 33 is in liquid form in case of filling operation, flowed into fine clearances and then is hardened afterwards, the filler material 33 may enter the fitted contacted part between the terminals 30, 31 of the discharge tube 29 and the terminals 27 and 28 of the casing 26 and it shows a problem that a poor electrical contact is produced.
In view of the foregoing, the present invention is completed, and it is an object of the present invention to provide a high-tension cable device capable of preventing a poor electrical contact between the additional function part such as a discharge tube assembled within the casing and the terminal of the casing.
The high-tension cable device of the present invention in order to accomplish the aforesaid object has an additional function part such as a series-gap forming discharge tube in the casing having at its one end a connector terminal capable of being engaged with a terminal of the ignition plug and having at its other end a power supplying terminal connected to a high-tension cable communicating with the power supplying side characterized in that at least one of the aforesaid connector terminal or the power supplying terminal is formed with a concave part fitted to and contacted with the connection part with the aforesaid additional function part and covering an entire connection part.
According to the present invention, at least one of the connector terminal at the casing to which the additional function part is assembled or the power supplying terminal is formed with a concave part fitted to and connected with a connection part of the additional function part and covering an entire connection part, so that even if filler material which is in a liquid form during filling and hardened after the filling is filled around the aforesaid functional part, the filler material may not enter the fitted and connected part between the terminal at the aforesaid casing and the connected part of the additional function part.
The present invention is characterized in that at least one of the aforesaid connector terminal or the power supplying terminal is formed with a concave part covering an entire connector part of the aforesaid additional function parts and having a threaded part in it and at the same time a threaded part is formed at an outer surface of the connecting part of the aforesaid additional function parts corresponding to the concave part.